The pollution was particularly bad in the Central district of downtown Hong Kong, where luxury retail brands and multinational companies pay among the highest rents in the world.

Anti-pollution activists said Hong Kong could not keep blaming the weather or factories in neighbouring mainland China for its recurring pollution problems.

“If Hong Kong did not produce air pollutants, the weather conditions would not be able to exacerbate or cause further consequences,” Clean Air Network campaign manager Erica Chan told AFP.

Emissions from local vehicles using old and dirty engines are among the main contributors to Hong Kong’s air pollution, she said.

The government announced revisions to its air quality objectives for the first time in 25 years in January, after University of Hong Kong research showed pollution-related illnesses killed more than 3,000 residents a year.